General Information
When a Relative System Response (RSR) dispatcher is used for car assignment to hall calls, the car is assigned to a hall call, after the hall call is received. Thus, if a large number of people arrive at a floor at the start of down-peak or noontime or at the start or end of a special event, there is a delay in the car assignment to the floor because the hall call must first be registered. This results in large waiting time to the passengers.
Also, often the car which stops at the floor becomes full, and some people are left out. Then they have to re-register the hall call, and another car has to be sent to pick up the remaining passengers. This causes irritation to passengers and more waiting time.
When the enhanced Relative System Response algorithm of the above-referenced, concurrently filed application Ser. No. 318,307 is used, the traffic is predicted in terms of passenger counts and car stop counts. The expected boarding rates are then calculated. This boarding rate is then used as the expected queue behind the hall call. Thus, when a car is selected for assignment to the hall call, if the car does not have enough spare capacity, an additional car is sent to the same hall call floor. However, this estimated queue size does not take into account the queue build up in the future and does not send a car based on any expected increase in queue size. The enhanced RSR may send one car to a floor, because it calculates the boarding rate to be low. But the actual queue may be large, because no car answered the hall call for a long time.
Similarly, even if two cars are sent to a floor, that may not be adequate if the crowd is building at a fast rate. When a crowd is present, if a car stops for hall call in that direction, the car will become full. So a car which is going to stop at a crowded floor should not be assigned for additional hall calls, until it makes a car call stop after the crowded floor. Otherwise, other hall calls assigned after the crowded floor will have to be later reassigned.
The varying RSR algorithm of the co-pending application Ser. No. 07/192,436 and the enhanced RSR algorithm of the concurrently filed application Ser. No. 318,307 park the empty cars at the first floor of the parking zones. Though a crowd is expected at some floors, cars are not parked at those floors due to the lack of any crowd prediction.
For further general background information on RSR elevator car assignment systems, either with set or variable bonuses and penalties, reference is had to assignee's U.S. Pat. No. 4,363,381 issued to Joseph Bittar on Dec. 14, 1982, and the above-referenced Ser. No. 07/192,436, respectively. These approaches are further discussed in the sub-section entitled "RSR Assignments of Prior Approaches" below.